The invention relates to the field of lithography at sub-micron scale. By projecting beams of atoms either of alkali type (e.g. Na, Li, or Cr) or of metastable type (He* or Ar*), atomic lithography makes it possible, via a mask, respectively to cause substance to be deposited on a substrate to be treated or to cause a pattern to be etched in a resin deposited on that substrate. The article by M. Kreis et al., published in Applied Physics, Vol. B63, 649 (1996), illustrates that type of technique.
Compared with the more conventional technique of photon lithography, atomic lithography presents advantages which relate to the implementation conditions and to the physical limits of these techniques:                the photon source, generally a UV laser, requires high brightness and means that are complex and expensive for producing photons at shorter and shorter wavelengths in order to increase the resolution of the installation (e.g. an Nd:YAG type laser for exciting a supersonic jet of xenon atoms);        a magnifying optical system (magnifying by a factor of 4 or 5) formed by multilayer mirrors of reflectivity that is selective in wavelength and of limited lifetime; and        pattern thickness is limited by the wavelength used, e.g. 157 nanometers (nm) for the above-mentioned xenon jet in devices for producing extreme UV radiation close to soft X-rays.        
Micro-lithographic techniques based on atomic optics use thermal or quasi-supersonic beams of atoms that are confined in a magneto-optical trap. In such techniques, the beam of atoms is collimated by laser cooling and it interacts with an optical mask. A mask of this type is generally formed by a standing lightwave that is blue-shifted relative to the atomic transition frequency, thus creating a periodic repulsive potential on the path of the atoms. Such a potential acts as a grating having a pitch equal to half the optical wavelength. Such applications are described, for example, in the article by E. M. Rasel published in Physical Review Letter, Vol. 75, 2633 (1995).
It is thus possible to deposit or etch a series of parallel lines on the substrate, or by using two crossed masks it is possible to obtain a periodic array of predetermined geometrical shape (square, rectangular, or lozenge-shaped).
The atomic technique is, by its very essence, not limited by the wavelength of the associated wave since it is of angstrom order, unlike the above-described optical methods. Nevertheless, atomic micro-lithography used in interaction with optical masks requires masking potential at a high level of intensity, and thus requires the lightwave that creates the potential to be of high intensity, in order to obtain significant disturbance of the trajectories of the atoms. Thus, such an installation is not flexible in use. In addition, the resolution that is obtained is limited by the performance of the mask used.